Radiation absorbing polymer, composition for radiation absorbing coating, radiation absorbing coating and application thereof as anti-reflective coating

ABSTRACT

A radiation absorbing polymer having chemically bonded thereto a radiation absorbing dye, which has high absorption at a predetermined wavelength radiation, which shows good adhesion to a substrate and good thin film-forming, which has no dependence upon resists, which is soluble in a solvent for photoresists but becomes insoluble after being baked; a composition for radiation absorbing coating containing this polymer, and a radiation absorbing coating such as an anti-reflective coating formed from this composition are disclosed. The radiation absorbing polymer comprises a copolymer containing at least both a recurring unit composed of a monomer containing a keto group and a divalent group (preferably a methylene group) in its side chain and a recurring unit composed of a monomer containing an organic chromophore bonded directly or through a linkage group to the main chain. This radiation absorbing polymer is dissolved in a solvent such as alcohol, aromatic hydrocarbon, ketone, ester, etc., and the resulting solution is applied to a wafer and baked to form a radiation absorbing coating such as an anti-reflective coating. On this coating is coated, for example, a chemically amplified resist. This coated substrate is then exposed to deep UV rays and is developed to form a fine resist pattern excluding the influence of standing wave.

This Application is a divisional of application Ser. No. 09/244,358,U.S. Pat. No. 6,468,718, filed Feb. 4, 1999.

TECHNICAL FIELD

This invention relates to a radiation absorbing polymer which haschemically bonded thereto an organic chromophore, a coating compositioncontaining the radiation absorbing polymer and an anti-reflectivecoating formed from the coating composition and, more particularly, to aradiation absorbing polymer capable of forming a radiation absorbingcoating such as an anti-reflective coating useful in manufacturingintegrated circuit elements by lithography, a composition containing theradiation absorbing polymer, and a radiation absorbing coating such asan anti-reflective coating formed from the composition.

BACKGROUND ART

In the field of manufacturing integrated circuit elements, patterningtechnology to form finer patterns by lithographic process has madeprogress and, in recent years, in order to attain a higher degree ofintegration, the development of patterning technology enabling quartermicron fine patterning has been studied. In such a lithographic process,a photoresist is applied to a substrate, a latent image of a maskpattern is created in the photoresist using a reduction projectionexposure apparatus, then the latent image is developed using a properdeveloper solution to obtain a patterned resist with the desired widthand pattern. However, many substrates used in the field of manufacturingintegrated circuit elements have such a high reflectivity that, uponexposure, exposing light passing through the photoresist layer isreflected on the surface of the substrates and is again incident intothe photoresist layer, which causes the problem that desired patternsare not obtained or that patterns with some defects are formed due toexposure by the reflected light of photoresist areas which are not to beexposed. These are called problems of standing wave or notching. Varioustechniques have been investigated to solve the problems caused by suchreflection. For example, there have been attempted a technique ofdispersing a dye having radiation absorption at the same exposurewavelength as in the photoresist, a technique of forming a radiationabsorbing coating of an inorganic compound such as titanium nitrideaccording to a CVD method, vacuum evaporation method or the like, atechnique of forming a radiation absorbing coating by applying adispersion or solution of a radiation absorbing dye in an organicpolymer solution on to a substrate, and a technique of forming aradiation absorbing coating by applying to a substrate a radiationabsorbing polymer having chemically bonded thereto a chromophore. Of theabove-described techniques, the technique of dispersing a radiationabsorbing dye in a photoresist has the problems of reduction inphotoresist sensitivity, thinning of the resist layer during developmentprocessing, sublimation of the dye upon baking, and the like. Thetechnique of using an inorganic anti-reflective coating has the variousproblems of difficulty in accurate control of coating thickness,difficulty of forming a coating with uniform coating thickness,requirement for a special apparatus for conducting, vapor deposition,poor adhesion with a resist film, a requirement for separately providinga step of transferring a pattern by dry etching, and the like. Further,the technique of dispersing a radiation absorbing dye in theanti-reflective coating involves the problems of separation of thepolymer and the dye from each other upon formation of theanti-reflective coating by spin-coating, elution of the dye into aresist solvent, sublimation of the dye into the resist layer uponbaking, and the like. On the other hand, the technique of using aradiation absorbing polymer does not involve such problems, and hencethis technique has been noted in recent years. Methods of usingradiation absorbing polymers as anti-reflective coatings and materialsto be used for the methods are described in, for example, JapaneseLaid-open Patent Publication Nos. H6-75378 and H6-118656, WO 9412912,U.S. Pat. Nos. 4,910,122 and 5,057,399, etc. Of the radiation absorbingpolymers, those polymers wherein a radiation absorbing chromophore ischemically bonded to the polymer skeleton have recently been consideredmost promising, and methods of using them and their application, havealready been studied. Particularly in the process of using radiationhaving a wavelength not longer than that of an eximer laser, ananti-reflective coating is considered to be necessary, and it has beendesired to provide an anti-reflective coating having good properties.

On the other hand, there exists a requirement that, upon formation of aphotoresist coating on a substrate having a large unevenness, anundercoating layer or an intermediate layer is first coated on thesubstrate to make the surface even for forming a resist image with highdimensional accuracy. Investigation for meeting such a requirement isalso necessary.

Formation of resist patterns using a radiation absorbing intermediatecoating such as an anti-reflective coating between a photoresist layerand a substrate before forming a resist pattern is conducted as follows.That is, a composition for a radiation absorbing coating such as ananti-reflective coating solution is first coated to a substrate and,after baking the coating to be made insoluble in a resist solvent, theresist coating is formed by a coating method on the radiation absorbingcoating, such as the anti-reflective coating, and is then subjected tothe processes of exposure, development processing, etc. to form a resistpattern, followed by removing the coating such as the anti-reflectivecoating in the resist-free areas, by dry etching or the like.

The above-described radiation absorbing polymers wherein a dye ischemically bonded to a skeletal polymer, generally have a low solubilityin solvents for resists, and hence solvents different from those usedfor resists, such as cyclohexanone, are often employed as a solvent forthe radiation absorbing polymer. In case that a solvent used for forminga radiation absorbing coating, such as an anti-reflective coating, isdifferent from that for resist, there may arise problems that processsteps for forming the anti-reflective coating in manufacturingintegrated circuits increase in number and, in some cases, properties ofthe resist layer themselves are adversely affected. In addition, in thecase that the anti-reflective coating and the photoresist layer areformed by using the same coating apparatus and the anti-reflectivecoating materials are insoluble in the solvent for resist, there arisesa problem that the anti-reflective coating material might beprecipitated due to the influence of mixing of the resist coating wasteand the anti-reflective coating solution. The precipitate thus formedmight close up pipes for waste liquor, or might scatter as fine powder,resulting in pattern defects. Further, an additional pipe line forfeeding a solvent for washing the backside and periphery of substratemight be required. As is described above, an anti-reflective coatingcomposition containing a low molecular weight dye dispersed in a polymerhas also been developed. Such composition, however, often causesunevenness in coating thickness when coated on a surface of a substratewith topography, that is, it provides poor coverage, which shoulddesired to be improved. In addition, in conducting the resist process ona substrate with areas with topography, coating of the resist is, insome cases, difficult or it is difficult to make the thickness of theresist uniform, due to difference in the level of the surface. There isalso a requirement on planarization of the substrate surface by afilm-forming material to get uniform thickness of the resist coatingformed thereon for improving the accuracy of the formed resist pattern,as well as preventing reflection. Thus, it has been desired to providean anti-reflecting coating material which can provide high performance,which enables one to control coverage properties on a surface of asubstrate with topography, which undergoes no change in the propertiesof the anti-reflective coating upon baking, and which is soluble in asolvent for the resist.

Further, it has eagerly been required to attain higher resolution in theresist process and, therefore, wavelength of radiation for exposingresists is being shifted to shorter wavelengths, and a process of usingKrF laser (248 nm) has been put into practice. However, since substratespresently used show high reflectivity for radiation of such shortwavelength and since thickness of a resist is being reduced with theenhancement of resolution, a radiation absorbing coating is desiredwhich can well prevent reflection even when used in a thin thickness inview of the dry etching process. Therefore, it is necessary to develop aradiation absorbing material which absorbs well the radiation of theshorter wavelength to be used, which shows no coating defects even whencoated in a thin thickness, and which can match with various kinds ofresists.

This invention is made to provide a radiation absorbing polymersatisfying these requirements, a composition containing such a radiationabsorbing polymer, and a radiation absorbing coating formed by using thecomposition.

That is, a first object of the present invention is to provide aradiation absorbing polymer which satisfies the above-described variousrequirements, that is, which shows high solubility in a resist solvent,which can form a radiation absorbing coating such as a conformalanti-reflective coating on a substrate with topography, which, in somecases, can fill up depressions on the surface of a substrate to make iteven, which shows a high anti-reflective effect, and which can form aresist pattern with good adhesion to the substrate and a resist layer,good dry etchability, high heat-resistance and excellent resolution.

A second object of this invention is to provide a composition which canform a radiation absorbing coating capable of satisfying theabove-described requirements.

A third object of the present invention is to provide a method forforming a radiation absorbing coating capable of satisfying theabove-described requirements.

The other object of this invention is to provide a radiation absorbingcoating and an anti-reflective coating capable of satisfying theabove-described requirements.

DISCLOSURE OF THE INVENTION

As a result of intensive investigations, the inventors have found that aradiation absorbing polymer satisfying the above-described requirementscan be obtained by using a monomer having a keto group in its side chainas a recurring unit of the radiation absorbing polymer.

That is, one aspect of the present invention is a radiation absorbingpolymer which has absorption at a predetermined wavelength radiation andwhich contains at least both a recurring unit having a keto group in itsside chain and represented by the following general formula (1) and arecurring unit having in its side chain an organic chromophore absorbinga predetermined wavelength radiation and represented by the followingformula (2):

wherein

R₁ and R₂-independently represent a hydrogen atom, an alkyl group orother organic group, and R₃ represents an organic group having at leastone carbonyl group;

wherein

R₄ and R₅ independently represent a hydrogen atom, an alkyl group, acarboxyl group or other organic group, and Y represents a group havingan organic chromophore having an absorption at a predeterminedwavelength radiation, said organic chromophore being bonded directly orthrough a linkage group to the carbon atom constituting the main chain.

Another aspect of the present invention is a composition for radiationabsorbing coating containing the above-described radiation absorbingpolymer.

A further aspect of the present invention is a method of forming aradiation absorbing coating by applying the composition for radiationabsorbing coating on a substrate and baking it.

A still further aspect of the present invention is a radiation absorbingcoating and an anti-reflective coating formed according to theabove-described method.

The present invention is described in more detail by the followingdescriptions which, however, should not be construed to limit the scopeof the present invention.

First, as is described above, the radiation absorbing polymer of thepresent invention is a radiation absorbing polymer containing at leastboth the recurring unit represented by the formula (1) and the recurringunit represented by the formula (2) and absorbing at a predeterminedwavelength of radiation. Preferred examples of the recurring unitrepresented by the formula 1 are those represented by the followingformula (3), (4) or (5). In the case that a plurality of keto groups arein the recurring unit represented by the following formula (3), (4) or(5), the radiation absorbing polymer shows improved solubility insolvents usually used for resists, due to the existence of the ketogroups and, in case that at least one hydrogen atom is bonded to themethylene group of the recurring unit, there results a hard coatingowing to the reaction with a cross linking agent based on the activityof the hydrogen atom.

wherein

R₁ and R₂ represent independently a hydrogen atom, an alkyl group orother organic group, R₆ represents an organic group containing at leastone carbonyl group, X₁ represents O, S, NR₇ or a straight, branched orcyclic alkylene group containing at least one carbon atom, R₇ representsa hydrogen atom or a substituted or non-substituted, phenyl or cyclic,straight or branched alkyl group.

wherein

R₁, R₂, R₈, R₉ and R₁₀ represent independently a hydrogen atom, an alkylgroup or other organic group.

wherein

R₁, R₂, R₁₂, R₁₃ and R₁₄ represent independently a hydrogen atom, analkyl group or other organic group, and R₁₁ represents a divalent group.

As monomers for constituting the recurring units represented by theabove-described formula 3 or 4, there are specifically illustrated thefollowing ones:

As the recurring unit represented by the above-described formula 5,there are illustrated, for example, those wherein R₁₁ represents —OR₁₅O—or —NHR₁₅O— (wherein R₁₅ represents one of substituted ornon-substituted, straight, branched or cyclic alkylene groups or asubstituted or non-substituted phenylene group), with those wherein R₁₅represents an alkylene group such as an ethylene group. As monomers forconstituting the recurring units represented by the above-describedformula 3 or 5, there are specifically illustrated the following ones:

On the other hand, the recurring unit represented by the above formula 2is more specifically exemplified by those represented by the followingformula 6 or 7:

wherein

R₄ and R₅ represent independently a hydrogen atom, an alkyl group, acarboxyl group or other organic group, and Ar is a chromophore whichabsorbs the predetermined wavelength radiation and represents one ofsubstituted or non-substituted benzene ring, condensed ring orheterocyclic ring groups bonded directly or through a linkage group tothe main chain carbon atom.

wherein

R₄ and R₅ represent independently a hydrogen atom, an alkyl group, acarboxyl group or other organic group, X₂ represents O, S, NR₁₆ or astraight, branched or cyclic alkylene group containing at least onecarbon atom, R₁₆ represents a hydrogen atom or a substituted ornon-substituted, phenyl group or cyclic, straight or branched alkylgroup and Ar₁ is a chromophore which has absorption at a predeterminedwavelength radiation and represents one of substituted ornon-substituted benzene ring, condensed ring or heterocyclic ring groupsbonded directly or through a linkage group to X₂.

Monomers used for constituting the recurring units represented by theabove formula 6 or 7 are exemplified by the following:

In addition, the radiation absorbing polymer of the present inventionmay contain other recurring units than those represented by the formulae(1) and (2) in addition to the recurring units represented by theformulae (1) and (2) in order to impart the polymer high radiationabsorbing property, high etching rate, good solubility for a particularsolvent, good storage stability, cross-linking property (curability) orother preferred properties. As monomers for constituting such otherrecurring units, usually acrylates or methacrylates are used forimparting solubility to the resulting polymer, and styrenes are used forincreasing Tg. Other specific examples of the other comonomers thanthose for constituting the recurring units of formulae 1 and 2, whichcan impart preferred properties, include methyl methacrylate, methylacrylate, 2-hydroxyethyl methacrylate, ethyl methacrylate,2-(methacryloyloxy)ethyl methacrylate, butyl methacrylate, t-butylmethacrylate, glycidyl methacrylate, methacrylic acid, acrylic acid,acrylonitrile, acrylamide, hydroxymethylacrylamide, 2-isocyanatoethylmethacrylate, 4-acetoxystyrene, 3-methyl-4-hydroxystyrene, styrene,vinyl chloride, ethyl vinyl ether, butyl vinyl ether, isobutyl vinylether, cyclohexyl vinyl ether, methyl vinyl ether, maleic anhydride,maleimide, N-substituted maleimide, vinyl acetate, 2-isocyanatoethylacrylate, etc. Of these, methyl methacrylate, methacrylic acid, methylacrylate, 2-hydroxyethyl methacrylate, hydroxymethylacrylamide, butylmethacrylate, t-butyl methacrylate, glycidyl methacrylate, methyl vinylether, butyl vinyl ether, etc. are preferred.

Main properties to be imparted by these comonomers are illustratedbelow. In the case of using together with organic chromophore, radiationabsorption is more enhanced by using, for example, 2-isocyanatoethylacrylate, maleic anhydride, maleimide, N-substituted maleimide,2-isocyanatoethyl methacrylate, etc. as the comonomers, etching rate isincreased by using, for example, methyl methacrylate, methyl acrylate,2-hydroxyethyl methacrylate, ethyl methacrylate, butyl methacrylate,t-butyl methacrylate, acrylic acid, vinyl chloride, etc., solubility forsolvents commonly used as solvents for photoresists such as propyleneglycol monomethyl ether acetate (PGMEA) or ethyl lactate is improved byusing, for example, 2-(methacryloyloxy)ethyl methacrylate, acrylic acid,4-acetoxystyrene, 3-methyl-4-hydroxystyrene, ethyl vinyl ether,butylvinyl ether, isobutyl vinyl ether, cyclohexylvinyl ether, methylvinyl ether, vinyl acetate, etc., cross-linking property (curability) isimproved by using, for example, 2-isocyanatoethyl acrylate,2-isocyanatoethyl methacrylate, methacrylic acid, glycidyl methacrylate,hydroxymethylacrylamide, etc., Tg is increased by using, for example,styrene, 3-methyl-4-hydroxystyrene, etc. However, the above-describedspecific comonomers and properties imparted by them are to be construedas merely illustrative and not limitative at all.

As the monomers constituting the recurring unit having in the side chainthereof an organic chromophore which absorbs a predetermined wavelengthradiation, there are illustrated, for example, those wherein a hydroxylgroup- or amino group-containing organic chromophore is chemicallybonded to the acid anhydride group or a carboxyl group bonded to themain chain.

Molecular weight and proportion of the recurring units of the radiationabsorbing polymer in accordance with the present invention can widely bevaried but, in the case of using as a material for forming radiationabsorbing coating, those which have a molecular weight of from about1,000 to about 500,000 and contain at least 5 mol %, based on the wholerecurring units, of the recurring unit represented by the formula 1 andat least 10 mol % of the recurring unit represented by the formula 2 arepreferred. More preferably, each of the recurring units represented bythe formulae 1 and 2 are contained in an amount of 15 mol % or morebased on the whole recurring units.

The radiation absorbing polymer of the present invention can be used as,for example, a material for bottom anti-reflective coating used inmanufacturing integrated circuits by dissolving the polymer in asolvent. In the case of employing ultraviolet or deep ultraviolet ray asan exposure source for manufacturing integrated circuits using theradiation absorbing polymer of the present invention, the polymerpreferably has a strong absorption in the wavelength region of from 180to 450 nm. In order to obtain such a radiation absorbing polymer, properrecurring unit or units are selected from the recurring unitsrepresented by the foregoing formula (2) and, if necessary, from therecurring units represented by the formula (1) or from the recurringunits other than those represented by the formulae (1) and (2). Use ofsuch properly selected recurring units represented by the formula (2),capable of strongly absorbing radiation of the exposure wavelength,enables the radiation absorbing polymer containing the recurring unitsto strongly absorb the radiation used for exposure, thereby reflectionof the exposure radiation from the substrate is prevented and adefect-free resist pattern is formed.

The composition for radiation absorbing coating of the present inventioncontains the above-described radiation absorbing polymer and comprisesthe radiation absorbing polymer and, if necessary, additives dissolvedin a proper solvent. As the solvent to be used for the composition ofthe present invention, any of those that have conventionally been usedfor forming a coating and can dissolve the radiation absorbing polymerand other additives may be used. As preferred examples of the solvents,there are illustrated γ-butyrolactone, cyclohexanone, dimethylacetamide,dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, ethyl lactate(EL), methoxy propanol (PGME), propylene glycol monomethyl ether acetate(PGMEA), methyl amyl ketone (MAK) or an optional mixture thereof. Ofthese, γ-butyrolactone, cyclohexanone, EL, PGME, PGMEA and a mixedsolvent of PGME and PGMEA are particularly preferable solvents.

Concentration of the radiation absorbing polymer in the composition canbe varied over a wide range depending upon the purpose of use of thecomposition and the thickness of the radiation absorbing coating. Forexample, in the case of use as an anti-reflective coating, it is usually20% by weight or less

As the additives to be contained in the composition for radiationabsorbing coating of the present invention, there are illustrated, forexample, conventionally known radiation absorbing compounds, surfactantsor silane series leveling agents for improving adhesion to a substrateand enhancing coating properties, and the like. In addition, in order toenhance cross-linking density upon formation of the coating, commonlyknown cross-linking agents and cross-linking auxiliaries may be added.As cross-linking agents and cross-linking auxiliaries, there arespecifically illustrated melamine compounds, substituted urea compounds,acid-generating agents which can generate acid upon being heated orirradiated to thereby accelerate cross linking, bisblocked isocyanates,blocked isocyanates and epoxy group-containing polymers, etc. Thesecross-linking agents or auxiliaries may be either low molecular weightcompounds or polymers. These cross-linking agents or auxiliaries aredesirably added in an amount of 0.1 to 50% by weight based on the weightof the radiation absorbing polymer. In the composition for radiationabsorbing coating may also be incorporated, if necessary, low molecularweight compounds or polymers other than the polymer of the presentinvention.

The radiation absorbing coating of the present invention containing theradiation absorbing polymer may be formed on, for example, a substrateby coating on a substrate a composition for radiation absorbing coatingobtained by dissolving the radiation absorbing polymer and, ifnecessary, desired additives in a proper solvent or, in some cases, byconducting the polymer-forming reaction on the substrate to therebydirectly form a coating of the reaction product on the substrate.

The radiation absorbing coating composition is coated on a substrate ina proper thickness depending upon its use. In the case of forming, forexample, an anti-reflective coating, it is coated on a substrate in adry thickness of 300 to 5,000 Å, by spin coating, cast coating, rollercoating or the like. After the coating procedure, the coating is bakedon a hot plate or in an oven to make it insoluble in a resist solvent.The baking is conducted at a temperature of about 90 to 260° C.,preferably 160° C. or above.

A photoresist is applied to the radiation absorbing coating, such as theanti-reflective coating thus formed on the substrate, in a predeterminedthickness, then prebaked to form a photoresist layer. As thephotoresist, either positive working or negative working photoresistscan be used. Typical examples of usable photoresists include a positiveworking photoresist comprising novolak resin and a quinonediazide typelight-sensitive agent, a chemically amplified resist, etc. which,however, are not limitative at all. Solvents for the photoresist includeEL, PGME, PGMEA, ketones, etc. Prebaking temperatures vary dependingupon the kind of photoresist to be used, but is usually about 30 toabout 200° C. The radiation for exposure of the photoresist can beselected from among visible light, UV rays, deep UV rays, KrF eximerlaser, argon fluoride (ArF) laser (193 nm), X-rays, electron beams, etc.As the radiation absorbing polymer used in radiation absorbing coatingto prevent the reflection from the substrate, those polymers whichabsorb the radiation of wavelengths required for exposure, as has beendescribed hereinbefore, are selected. After exposure, the photoresist issubjected to development with a developer solution after optionallypost-exposure baking, a resist pattern thus being formed. The radiationabsorbing coating such as the anti-reflective coating is then dry etchedusing gas plasma such as oxygen plasma to thereby form a defect-freeresist pattern that serves to process or treat the substrate.Additionally, as the developer solution, there may be used knowndevelopers such as an alkaline aqueous solution which contains a metalhydroxide, an organic amine or the like dissolved therein.

By selecting the processing conditions, the composition for radiationabsorbing coating of the present invention may also be used as a coatingwhich functions to prevent reflection of radiation and to preventadverse mutual action between the substrate and the resist or to preventthe adverse action of materials used in the resist or substancesproduced upon exposure of the resist on the substrate. Further, it maybe used as a coating for planarizing the surface of the substrate onwhich a pattern has already been formed (substrate having topography) byfill up depressions on the surface before coating a photoresist thereonto thereby enhance uniformity in the thickness of the coating, such as aphotoresist to be coated thereon.

Additionally, in the case of using the radiation absorbing coating ofthe present invention as a coating which planarizes the substratesurface, it is proposed to slightly reduce the glass transitiontemperature (Tg) of the radiation absorbing polymer to cause some flowupon baking and, after being completely solidified, make the coatinginsoluble in resist solvents. The slight reduction in Tg may beattained, for example, by slightly reducing the cross-linking ability ofthe radiation absorbing polymer upon being heated. In order to impart tothe polymer the function flat XXXX the surface of the substrate, thereare various techniques of, for example, properly selecting this degreeof polymerization of the radiation absorbing polymer, concentration ofthe radiation absorbing polymer in the composition or substituents inthe recurring units represented by the formula (1) or (2) and properlyselecting the proportion of the recurring units represented by theformulae (1) and (2) in the polymer and a type of comonomer other thanthose represented by the formula (1) or (2), or properly selecting thetype of additives.

The coating composition for radiation absorbing of the present inventionis soluble in a solvent for a photoresist. Therefore, it enables one touse the same coating apparatus, the same waste liquor apparatus and thesame rinsing solution as those used for the resist. In addition, theanti-reflective coating using the radiation absorbing polymer of thepresent invention which shows a high absorption of DUV (248 nm) canpreferably be used as an anti-reflective coating for chemicallyamplified resists sensitive to DUV. Further, the radiation absorbingcoating of the present invention has such a low dependence upon resiststhat anti-reflective coating materials are not required to be changedwhen resists are changed in the manufacture of IC, and therefore, noprocess changes have to be evalusted, which is extremely advantageousfor users. For example, AZ®-BARLi® coating manufactured by ClariantCorp., a commercially available anti-reflective coating material,designed for i-line (365 nm) exposure is very soluble in cyclohexanone,but is barely soluble in a resist solvent and has, therefore, the defectthat used the same coating apparatus as that for coating resist isdifficultly used upon applying the anti-reflective coating compositionor upon edge rinsing. In addition, though AZ®-BARLi® coating itselfabsorbs DUV, it has such a resist dependence that, in some cases,footing or undercut is observed in the profile of a resulting resistpattern. The radiation absorbing polymer of the present invention alsohas the feature that, while it is soluble in a resist solvent, it formsa film insoluble in the resist solvent and, is also, insoluble in anaqueous alkaline developer solution for resists, due to being heated ata proper temperature after coating on a substrate. Therefore, theradiation absorbing coating such as the anti-reflective coating of thepresent invention never suffers dissolution when a photoresist coatingcomposition Is coated thereon or when wet a development processing isconducted after exposure. Still further, the radiation absorbing coatingof the present invention has the feature that, when a resist pattern isused as an etching mask, it can easily be removed by dry etching.

Additionally, the radiation absorbing polymer of the present inventionmay be obtained according to various known synthesizing processes. Forexample, there is illustrated a process of copolymerizing a monomerhaving a keto group in the side chain and corresponding to the recurringunit represented by the foregoing formula (1) with a monomer having anorganic chromophore and corresponding to the recurring unit representedby the foregoing formula (2). The monomer having an organic chromophoremay easily be obtained by known synthesis processes, for example, byconverting a hydroxyl group- or amino group-containing organicchromophore compound to its acrylate or acrylamide. As the process forobtaining the radiation absorbing polymer, the above-describedcopolymerization process is the most popular. However, it is alsopossible to introduce a radiation absorbing group into a polymer by thereaction between a polymer having a reactive group and an organicchromophore compound having a hydroxyl group, an amino group, or thelike.

In the present invention, polymerization may be conducted in a propersolvent using a free radical or ionic reaction initiator. The resultingcopolymer may be of various structures such as a random copolymer or ablock copolymer. As preferred solvents for the polymerization, there areillustrated toluene, tetrahydrofuran, benzene, dimethylformamide,dimethylsulfoxide, ethyl lactate, propylene glycol monomethyl-etheracetate (PGMEA), cyclopentanone, cyclohexanone, butyrolactone,2-heptanone, ethyl-3-ethoxypropanate, ethylene glycol monoethyl acetate,methyl-3-methoxypropanate, etc. These solvents may be used alone or incombination of two or more of them.

As specific examples of the reaction initiators, there are illustrated2,2′-azobis(isobutyronitrile)(AIBN),2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis(2-cyclopropylpropionitrile), 2,2′-azobis(2,4-dimethyl valeronitrile),2,2′-azobis(2,4-dimethylpentanenitrile),1,1′-azobis(cyclohexanecarbonitrile), benzoyl peroxide, t-butyl peroxybenzoate, di-t-butyl diperoxy phthalate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy pivalate, t-amyl peroxy pivalate, butyllithium, etc. However, initiators are not limited only to these.

These polymers may be separated from the solvent, then again dissolvedin a proper solvent to prepare an anti-reflective coating composition ora composition for radiation absorbing coating or, if the solvent used inthe synthesis reaction can be utilized as a solvent for theanti-reflection coating composition or composition for radiationabsorbing coating, it may directly be used as the anti-reflectivecoating composition or composition for radiation absorbing coatingwithout separating the polymer, or the reaction solution may directly beapplied to a substrate such as a wafer after completion of the reaction.Additionally, the anti-reflective coating composition or composition forradiation absorbing coating is desirably subjected to filtration using,for example, using a 0.5, 0.2 or 0.1 micron (μm) filter to therebyremove insoluble fine particles. The filtered solution may directly beapplied to a substrate such as a wafer.

Molecular weight of the thus obtained polymer varies depending uponpolymerization time, reaction temperature, concentrations of usedmonomers and initiators, kind of reaction medium, etc. and can easily becontrolled by properly selecting these parameters. Polymers having anarrow molecular weight distribution may be obtained by employing ionicpolymerization.

Molar ration of the comonomers in the radiation absorbing polymer isdecided based on reaction rate of each monomer and employed reactionconditions. The radiation absorption and refractive index of finalpolymer to a desired wavelength radiation is quite important indetermining whether the polymer can be used as a bottom anti-reflectivecoating or the like or not. Radiation absorption of the coating ispreferably in the range of from 2 to 40 per micron in thickness, with 5to 25 being more preferred. Copolymers composed of three or more typesof comonomers also required to provide such absorption. Too strong ortoo weak absorption fails to provide favorable results as ananti-reflective coating. Radiation absorbing properties required foranti-reflective coating materials also depend upon radiation absorbingproperties and refractive index of the photoresist material to be coatedthereon. Most preferably, the refractive index of the anti-reflectivecoating is the same as that of the photoresist layer to be coatedthereon and, if not, the two indexes are preferably as close as possibleto each other. Since radiation absorbing properties of theanti-reflective coating materials are determined by the radiationabsorbing properties and molar ratio of the chromophore-containingmonomer, the proportion of the chromophore-containing monomer in mol %is important for the anti-reflective coating material. In the presentinvention, this proportion can easily be controlled by adjusting thecharging proportion of the chromophore-containing monomer, and a polymerwith the desired values can be prepared.

BEST MODE FOR PRACTICING THE INVENTION

The present invention is now described in more details by reference tothe following Examples. These examples, however, are only illustrativeto explain the present invention and are not intended to limit the scopeof the present invention.

SYNTHESIS EXAMPLE 1 Synthesis of 9-Methacryloyloxymethylanthracene

87.5 g (0.42 mol) of 9-hydroxymethylanthracene was added to 500 ml ofethyl acetate at room temperature. To this was further added 7.3 g (60millimols) of 4-dimethylaminopyridine under stirring, and 83 g (0.54mol) of methacrylic anhydride was dropwise added thereto. Thereafter,the reaction mixture solution was stirred at 60° C. for about 4 hoursuntil the reaction was completed. After completion of the reaction, thereaction product was cooled to room temperature, and ethyl acetate wasadded thereto. The organic layer was washed with, successively, analkaline water and water, then subjected to distillation under reducedpressure to remove the organic solvent and obtain a solid end product.Yield was 80 g (73%). This product was identified by measurement of theUV absorption in methanol and NMR. The UV absorption measurementrevealed that the molar extinction coefficient at 248 nm was 1.05×10⁵.¹H-NMR(DMSO-d6), (400 MHz) measurement showed signals at 1.82(s,3H),5.59(s,1H), 5.9(s,1H), 6.2(s,2H), 7.49-7.7(m,4H), 8.12(m,2H), 8.4(m,2H)and 8.67(s,1H).

SYNTHESIS EXAMPLE 2 Synthesis of 1-Methacryloylaminoanthracene

25 g (0.13 mol) of 1-aminoanthracene was dissolved in 120 ml of ethylacetate at room temperature. To this solution was added 0.61 g (5millimols) of 4-dimethylaminopyridine and, under stirring, a mixedsolution of 24.6 g (0.16 mol) of methacrylic acid anhydride and 30 ml ofethyl acetate was added dropwise thereto over about 5 minutes.Thereafter, the reaction mixture solution was stirred at 50° C. for 3hours, then cooled to room temperature, followed by collecting theprecipitate formed by filtration. The precipitate was washed twice withethyl acetate, then dried under vacuum to obtain the end product of1-methacryloylaminoanthracene. Yield was 18.6 g (60% ). Further, about 9g of the end product was obtained from the filtrate. Measurement of theU absorption in methanol revealed that molar extinction coefficient at248 nm was 4.1×10⁴.

EXAMPLE 1

55.2 g (0.2 mol) of 9-methacryloyloxymethylanthracene and 42.8 g (0.2mol) of acetylacetoxyethyl methacrylate were dissolved in 500 ml oftetrahydrofuran (THF), and 3.28 g (20 millimols) ofazobisisobutyronitrile (AIBN) was added thereto as a radical initiator.Then, the mixture was stirred at room temperature for 15 minutes whileintroducing thereinto nitrogen, followed by heating the reaction mixturesolution at a reflux temperature for 10 hours. Thereafter, the reactionsolution was cooled to room temperature, then poured into isopropanol(IPA) to form a precipitate. The precipitate was collected byfiltration, washed with IPA, and dried in vacuo at 50° C. to obtain apolymer (hereinafter referred to as “polymer A”). Yield was 78 g (82%).¹H-NMR(DMSO-d6) measurement revealed the presence of a proton on thearomatic ring or anthracene (6.5-8.3 ppm) and a methylene proton boundto anthracene (5.2-6.3 ppm). Further, the integral ratio of proton ofethyl derived from acetylacetoxyethyl methacrylate (—OCH₂CH₂O—, 3-4 ppm)revealed that the molar ratio of 9-methacryloyloxymethylanthracenemonomer to acetylacetoxyethyl methacrylate in the polymer was about1.06:1. GPC analysis using dimethylformamide as a mobile phase andpolyethylene oxide as a standard substance revealed that polymer A had aweight average molecular weight, Mw, of 17,000, a number averagemolecular weight, Mn, of 8,430, and degree of dispersion, Mw/Mn, of2.03. Separately, polymer A was dissolved in PGMEA in a concentrationcapable of being coated on a silicon wafer in a thickness of about 100nm by spin coating, coated on a silicon wafer, and baked at 200° C. for60 seconds. The optical absorption coefficient (k value) at 248 nm ofthe thus formed coating was measured as 0.58, using a spectralellipsometer. When polymer A was mixed with PGMEA in a proportion of 10wt % and stirred at room temperature, the polymer was completelydissolved.

EXAMPLE 2

Polymers were synthesized in the same manner as in Example 1 except forchanging charging the ratio of 9-methacryloyloxymethylanthracene (MAOMA)and acetylacetoxyethyl methacrylate (AAEM) to the values described insynthesis numbers 1 and 2 shown in Table 1. Copolymerization ratios(molar ratio) of MAOMA to AAEM of the thus obtained polymers weremeasured and confirmed. The optical absorption coefficients k of thepolymer coating at 248 nm were measured using a spectral ellipsometer.Results of the measurements are shown in Table 1. Further, elution testsrevealed that every polymer was readily soluble in a resist solvent suchas PGMEA. From these results, it is seen that the present invention canprovide polymers showing a high absorption and being soluble in a resistsolvent with a good reproducibility.

TABLE 1 molar ratio in molar ratio of polymer based on monomer NMRspectrum value of k Synthesis No. MAOMA:AAEM MAOMA:AAEM (248 nm) 1 0.5:10.55:1 0.48 2 0.6:1  0.5:1 0.51 3-1   1:1 1.06:1 0.58 (Example 1) 3-2  1:1  1.1:1 0.59 (repeat of Example 1)

EXAMPLE 3

52.2 g (0.2 mol) of 1-methacryloylaminoanthracene and 42.8 g (0.2 mol)of acetylacetoxyethyl methacrylate were dissolved in 500 ml oftetrahydrofuran (THF) at room temperature, and 3.28 g (20 millimols) ofazobisisobutyronitrile (AIBN) was added thereto as a radical initiator.Then, the mixture was stirred at room temperature for 15 minutes whileintroducing thereinto nitrogen, followed by heating the reaction mixturesolution at a reflux temperature for 10 hours. Thereafter, the reactionsolution was cooled to room temperature, then poured into isopropanol(IPA) to form a precipitate. The precipitate was collected byfiltration, washed with IPA, and dried in vacuo at 50° C. to obtain apolymer. Yield was 82 g (89%). The integral ratio of proton in theanthracene moiety to proton of ethyl derived from acetylacetoxyethylmethacrylate (—OCH₂CH₂O—) by ¹H-NMR(DMSO-d6) measurement revealed thatthe molar ratio of the two monomers in the polymer was about 1:1. GPCanalysis using dimethylformamide as a mobile phase and polyethyleneoxide as a standard substance revealed that the obtained polymer had aweight average molecular weight, Mw, of 35,000, a number averagemolecular weight, Mn, of 15,200, and degree of dispersion, Mw/Mn, of2.3. Separately, this polymer was formed into a coating by baking at200° C. for 60 seconds. The optical absorption coefficient, k at 248 nmof the thus formed coating was measured as 0.4 using a spectralellipsometer.

EXAMPLE 4

41.4 g (0.15 mol) of MAOMA, 32.1 g (0.15 mol) of AAEM and 15 g (0.15mol) of methyl methacrylate were dissolved in 500 ml of tetrahydrofuran(THF) at room temperature, and 3.28 g (20 millimols) ofazobisisobutyronitrile (AIBN) was added thereto as a radical initiator.Then, the mixture was stirred at room temperature for 15 minutes whileintroducing thereinto nitrogen, followed by heating the reaction mixturesolution at a reflux temperature for 10 hours. Thereafter, the reactionsolution was cooled to room temperature, then poured into isopropanol(IPA) to form a precipitate. The precipitate was collected byfiltration, washed with IPA, and dried in vacuo at 50° C. to obtain apolymer (hereinafter referred to as “polymer B”). Yield was 68.8 g(80%). GPC analysis using dimethylformamide as a mobile phase andpolyethylene oxide as a standard substance revealed that the obtainedpolymer had a weight average molecular weight, Mw, of 30,000, a numberaverage molecular weight, Mn, of 14,300, and degree of dispersion,Mw/Mn, of 2.1. Separately, this polymer was formed into a coating bybaking at 200° C. for 60 seconds. The optical absorption coefficient kat 248 nm of the thus formed coating was measured as 0.53 using aspectral ellipsometer. Results of elution test showed that the polymerhad a high solubility in resist solvents such as PGMEA,PGME and EL.

EXAMPLE 5

Preparation of radiation absorbing composition 6 g of the polymer Aobtained in Example 1 was dissolved in 100 g of PGMEA at roomtemperature with stirring and, after the polymer was completelydissolved, this solution was filtered through a 0.1-micron filter toobtain composition C for radiation absorbing coating. Separately, inthis composition C for radiation absorbing coating were dissolvedhexamethoxymethylmelamine (20 wt % based on polymer A) and2,4-bistrichloromethyl-6-styryl-s-triazine (2 wt % based on polymer A),and the resulting solution was filtered through a 0.1-micron filter toobtain composition D for radiation absorbing coating.

Further, 5 g of polymer B obtained in Example 4 was dissolved in 100 gof PGMEA at room temperature with stirring, and this solution was mixedwith 15 wt % based on the polymer of CORONATE® 2507 (blockedbisisocyanate; manufactured by Nippon Polyurethane K.K.) and, afterstirring for a while, the mixture was filtered through a 0.1-micronfilter to obtain composition E for radiation absorbing coating.

COMPARATIVE EXAMPLE 1

AZ®-BARLi® solution for forming an anti-reflective coating sold byClariant Corp. was coated on to a 4-inch silicon wafer by spin coatingunder proper conditions. The thus obtained sample was used for thefollowing experiments for comparison.

EXAMPLE 6

The compositions C, D and E for radiation absorbing coating prepared inExample 5 were respectively spin coated on to a 4-inch silicon wafersunder proper conditions. The thus obtained samples were used in thefollowing experiments for comparison.

EXAMPLE 7 Experiment for Comparing Rinsing Property Before Baking

The rinsing properties of the radiation absorbing coating were examinedby dropping a rinsing solution (PGME:PGMEA=70:30 (by weight)) for 10seconds, 20 seconds or 30 seconds onto a non-baked composition forradiation absorbing coating placed on a silicon wafer on a spin coaterrotating at 800 rpm. As a result, it was found that radiation absorbingcoatings formed from the compositions C, D and E for radiation absorbingcoating of the present invention were completely removed by the10-second rinsing, whereas a comparative film of AZ®-BARLi® coatingprepared by a comparative examination 1 was removed only partly evenwith a 30-second rinsing.

EXAMPLE 8 Experiments for Comparing Coverage

A resist pattern was previously formed on a silicon wafer, baked at ahigh temperature of about 250° C. to make the resist pattern insolublein a resist solvent, and platinum was vapor deposited thereon to preventadverse mutual action between the resist pattern and the composition forradiation absorbing coating and to facilitate observation under ascanning electron microscope (SEM). Thereafter, each of the compositionsC, D and E for radiation absorbing coating prepared in Example 5 wascoated onto the silicon wafer having a difference in surface level. Onthe other hand, AZ®-BARLi® coating manufactured by Clariant Corp. wassimilarly coated for comparison. These samples were baked on a hot plateat 100° C. for 90 seconds, then cross sections of the patterns wereobserved under the scanning electron microscope (SEM). As a result, itwas found that films obtained from the radiation absorbing polymers ofthe present invention were formed along the pattern form, thus showingthe same coverage property as AZ®-BARLi® film.

It was also found that some of the compositions for radiation absorbingcoating obtained from polymers having Tg value lowered by changing themonomer ratio can be coated and fill the depressions of the patternedsurface, by baking at a proper temperature of, for example, lower thanthe cross linking temperature to fluidize the polymer layer, thenraising the baking temperature so as to cross link the polymer. Suchcoating can generally be used as a leveling coating.

EXAMPLE 9 Experiment of Dissolution of Baked Anti-reflective CoatingInto a Resist Solvent

The composition E for radiation absorbing coating of the presentinvention was coated onto a silicon wafer at a in dry thickness of 1000Å, and was baked at a temperature of 180° C., 200° C. or 220° C. Aresist solvent of EL, PGMEA or MAK was dropped onto the baked coatingsand, after two minutes, the dropped solvent was wiped off to measure theamount of coating removed. Results thus obtained are shown in Table 2.It is seen from the results shown in Table 2 that the radiationabsorbing coating of the present invention formed by using the radiationabsorbing polymer soluble in the resist solvents and baking at asuitable temperature does not undergo change of the coating itself, suchas being dissolved in a resist composition, when a photoresist is formedthereon. In addition, when a developer solution (2.38 wt % aqueoussolution of tetramethylammonium hydroxide) was dropped onto each of thecoatings to measure the amount of removed coating in the same manner asdescribed above, there were obtained similarly excellent results.

TABLE 2 Baking temperature 180° C. 200° C. 220° C. E L 570 Å 70 Å  5 ÅPGMEA 1050 Å  60 Å −1 Å MAK 670 Å 35 Å −1 Å

EXAMPLE 10 Experiments of Testing Resist Pattern

Each of the radiation coating compositions D and E of the presentinvention was coated onto a silicon wafer at a dry thickness of about600 Å, and baked at 220° C. for 60 seconds to form anti-reflectivecoatings. Then, AZ® DX1100P, resist for DUV manufactured by ClariantJapan. was coated thereon in a thickness of 0.75 micron, patternwiseexposed and developed under predetermined conditions to form a resistpattern on each of the anti-reflective coatings. For comparison, aresist pattern was formed in the same manner on an anti-reflectivecoating composed of AZ®-BARLi® coating at a in thickness of 1200 Å.Observation of the cross section of each of the thus obtained resistpatterns under SEM revealed that the resist patterns formed by using theanti-reflective coatings of the present invention had higher resolutionthan that of AZ®-BARLi® film, no footing and no undercut. On the otherhand, the resist pattern formed by using AZ®-BARLi® coating showedfooting. The footing phenomenon may be attributed to adverse mutualaction between an acid generated in the exposed areas and the AZ®-BARLi®anti-reflective coating.

Pattern tests conducted by using other DUV photoresists on thereflective coatings of the present invention demonstrated good results.

EXAMPLE 11 Experiment of Comparing Etchability

Anti-reflective coating films obtained from the radiation absorbingcomposition of the present invention and an anti-reflective coating filmobtained from AZ®-BARLi® coating were formed in the same thickness fromeach other, baked at 220° C., and subjected to an etching test using adry etching apparatus. As a result of comparing the etch rate of eachcoating film, it was found that the polymer films of the presentinvention were etched at about the same etching rate as the AZ®-BARLi®film, with some of the polymer films of the present invention beingetched at somewhat faster rate than the film of AZ®-BARLi® film.

Effect of the Invention

As has been described hereinbefore, the radiation absorbing polymer ofthe present invention which contains a dye moiety having an absorptionat a proper wavelength shows a good radiation absorption for a radiationof the wavelength, enables one to form an anti-reflective coating with agood adhesion and, since it is soluble in a solvent to be used as aresist solvent, the same coating apparatus, the same waste liquorapparatus, and the same rinsing solution can be used as those forphotoresists in practicing the resist process, thus unnecessaryprocesses or equipment being eliminated.

In addition, the radiation absorbing polymer of the present inventioncan easily be formed into a film, and can be made insoluble in resistsolvents by heating at a proper temperature after being coated. Hence,it enables one to form a radiation absorbing coating such as ananti-reflective coating which is not dissolved in a resist compositionor a developer solution for resist during formation of a photoresistlayer or during development processing and which can be easily removedby dry etching, thus being well adapted for the resist process.

Further, in the case of coating the composition for radiation absorbingcoating of the present invention on a substrate with topography, thecomposition shows such good coverage that a mask pattern with highresolution can be formed on the substrate with topography. Stillfurther, in the resist process, it is sometimes required to improve theprocess latitude of the resist by planarization of a substrate. Thecomposition for radiation absorbing coating of the present invention canlevel the uneven surface using copolymers obtained by properly adjustingthe copolymerization ratio of copolymers, selection of the kinds ofcomonomer, constitution, baking temperature, etc., thus being capable offinding a wide application.

Still further, even in the case of using DUV photoresists posing severerequirements on a substrate, the anti-reflective coating can be used asone for plural DUV photoresists due to the low dependence of theradiation absorbing coating of the present invention.

Industrial Applicability

As has been described hereinbefore, the radiation absorbing polymer andthe composition for radiation absorbing coating of the present inventionare preferably used as a material for forming a radiation absorbingcoating, particularly an anti-reflective coating, in manufacturingintegrated circuit elements.

What is claimed is:
 1. A radiation absorbing polymer which absorbs apredetermined wavelength radiation and which contains at least both arecurring unit represented by the following formula (1) and a recurringunit represented by the following formula (2):

wherein R₁ and R₂ independently represent a hydrogen atom or an alkylgroup, and R₃ represents an organic group having at least one carbonylgroup;

wherein R₄ and R₅ independently represent a hydrogen atom, an alkylgroup or a carboxyl group, and Y represents a group having an organicchromophore having an absorption at a predetermined wavelengthradiation, said organic chromophore being bonded directly or through alinkage group to the carbon atom constituting the main chain, whereinsaid recurring unit represented by the formula (1) is a recurring unitrepresented by (a) the following formula (4):

wherein R₁, R₂, R₈, R₉ and R₁₀ represent independently a hydrogen atomor an alkyl group, or (b) the following formula (5):

wherein R₁, R₂, R₁₂, R₁₃ and R₁₄ represent independently a hydrogen atomor an alkyl group, and R₁₁ represents a divalent group.
 2. The radiationabsorbing polymer described in claim 1 which absorbs a predeterminedwavelength radiation, wherein R₁₁ in formula (5) represents —OR₁₅O—group, wherein R₁₅ represents one of substituted or non-substituted,straight, branched or cyclic alkylene groups or a substituted ornon-substituted phenylene group.
 3. The radiation absorbing polymerdescribed in claim 2 which absorbs a predetermined wavelength radiation,wherein R₁₅ represents an ethylene group.
 4. The radiation absorbingpolymer described in claim 1 which absorbs a predetermined wavelengthradiation, wherein R₁₁ in formula (5) represents —NHR₁₅O— group, whereinR₁₅ represents one of substituted or non-substituted, straight, branchedor cyclic alkylene groups or a substituted or non-substituted phenylenegroup.
 5. The radiation absorbing polymer described in claim 4 whichabsorbs a predetermined wavelength radiation, wherein R₁₅ represents anethylene group.
 6. The radiation absorbing polymer described in claim 1which absorbs a predetermined wavelength radiation, wherein saidrecurring unit represented by the formula (2) is a recurring unitrepresented by the following formula (6):

wherein R₄ and R₅ represent independently a hydrogen atom, an alkylgroup or a carboxyl group, and Ar is a chromophore which has absorptionat a predetermined wavelength radiation and represents one ofsubstituted or non-substituted benzene ring, condensed ring orheterocyclic ring groups bonded directly or through a linkage group tocarbon atom constituting the main chain.
 7. The radiation absorbingpolymer described in claim 1, wherein said recurring unit represented bythe formula (2) is a recurring unit represented by the following formula(7):

wherein R₄ and R₅ represent independently a hydrogen atom, an alkylgroup or a carboxyl group, X₂ represents O, S, NR₁₆ or a straight,branched or cyclic alkylene group containing at least one carbon atom,R₁₆ represents a hydrogen atom or a substituted or non-substituted,phenyl group or cyclic, straight or branched alkyl group and Ar₁ is achromophore which has absorption at a predetermined wavelength radiationand represents one of substituted or non-substituted benzene ring,condensed ring or heteroyclic ring groups bonded directly or through alinkage group to X₂.
 8. The radiation absorbing polymer described inclaim 2 which absorbs a predetermined wavelength radiation, wherein saidrecurring unit represented by the formula (2) is a recurring unitrepresented by the following formula (6):

wherein R₄ and R₅ represent independently a hydrogen atom, an alkylgroup or a carboxyl group, and Ar is a chromophore which has absorptionat a predetermined wavelength radiation and represents one ofsubstituted or non-substituted benzene ring, condensed ring orheterocyclic ring groups bonded directly or through a linkage group tocarbon atom constituting the main chain.
 9. The radiation absorbingpolymer described in claim 3 which absorbs a predetermined wavelengthradiation, wherein said recurring unit represented by the formula (2) isa recurring unit represented by the following formula (6):

wherein R₄ and R₅ represent independently a hydrogen atom, an alkylgroup or a carboxyl group, and Ar is a chromophore which has absorptionat a predetermined wavelength radiation and represents one ofsubstituted or non-substituted benzene ring, condensed ring orheterocyclic ring groups bonded directly or through a linkage group tocarbon atom constituting the main chain.
 10. The radiation absorbingpolymer described in claim 4 which absorbs a predetermined wavelengthradiation, wherein said recurring unit represented by the formula (2) isa recurring unit represented by the following formula (6):

wherein R₄ and R₅ represent independently a hydrogen atom, an alkylgroup or a carboxyl group, and Ar is a chromophore which has absorptionat a predetermined wavelength radiation and represents one ofsubstituted or non-substituted benzene ring, condensed ring orheterocyclic ring groups bonded directly or through a linkage group tocarbon atom constituting the main chain.
 11. The radiation absorbingpolymer described in claim 5 which absorbs a predetermined wavelengthradiation, wherein said recurring unit represented by the formula (2) isa recurring unit represented by the following formula (6):

wherein R₄ and R₅ represent independently a hydrogen atom, an alkylgroup or a carboxyl group, and Ar is a chromophore which has absorptionat a predetermined wavelength radiation and represents one ofsubstituted or non-substituted benzene ring, condensed ring orheterocyclic ring groups bonded directly or through a linkage group tocarbon atom constituting the main chain.
 12. The radiation absorbingpolymer described in claim 2, wherein said recurring unit represented bythe formula (2) is a recurring unit represented by the following formula(7):

wherein R₄ and R₅ represent independently a hydrogen atom, an alkylgroup or a carboxyl group, X₂ represents O, S, NR₁₆ or a straight,branched or cyclic alkylene group containing at least one carbon atom,R₁₆ represents a hydrogen atom or a substituted or non-substituted,phenyl group or cyclic, straight or branched alkyl group and Ar₁ is achromophore which has absorption at a predetermined wavelength radiationand represents one of substituted or non-substituted benzene ring,condensed ring or heterocyclic ring groups bonded directly or through alinkage group to X₂.
 13. The radiation absorbing polymer described inclaim 3, wherein said recurring unit represented by the formula (2) is arecurring unit represented by the following formula (7):

wherein R₄ and R₅ represent independently a hydrogen atom, an alkylgroup or a carboxyl group, X₂ represents O, S, NR₁₆ or a straight,branched or cyclic alkylene group containing at least one carbon atom,R₁₆ represents a hydrogen atom or a substituted or non-substituted,phenyl group or cyclic, straight or branched alkyl group and Ar₁ is achromophore which has absorption at a predetermined wavelength radiationand represents one of substituted or non-substituted benzene ring,condensed ring or heterocyclic ring groups bonded directly or through alinkage group to X₂.
 14. The radiation absorbing polymer described inclaim 4, wherein said recurring unit represented by the formula (2) is arecurring unit represented by the following formula (7):

wherein R₄ and R₅ represent independently a hydrogen atom, an alkylgroup or a carboxyl group, X₂ represents O, S, NR₁₆ or a straight,branched or cyclic alkylene group containing at least one carbon atom,R₁₆ represents a hydrogen atom or a substituted or non-substituted,phenyl group or cyclic, straight or branched alkyl group and Ar₁ is achromophore which has absorption at a predetermined wavelength radiationand represents one of substituted or non-substituted benzene ring,condensed ring or heterocyclic ring groups bonded directly or through alinkage group to X₂.
 15. The radiation absorbing polymer described inclaim 5, wherein said recurring unit represented by the formula (2) is arecurring unit represented by the following formula (7):

wherein R₄ and R₅ represent independently a hydrogen atom, an alkylgroup or a carboxyl group, X₂ represents O, S, NR₁₆ or a straight,branched or cyclic alkylene group containing at least one carbon atom,R₁₆ represents a hydrogen atom or a substituted or non-substituted,phenyl group or cyclic, straight or branched alkyl group and Ar₁ is achromophore which has absorption at a predetermined wavelength radiationand represents one of substituted or non-substituted benzene ring,condensed ring or heterocyclic ring groups bonded directly or through alinkage group to X₂.